A clamping ring and temperature regulated platen for clamping a wafer to the platen and regulating the temperature of the wafer. The force of the clamping ring against the wafer is produced by the weight of the clamping ring. A roof shields all but a few contact regions of the interface between the wafer and clamp from receiving depositing particles so that a coating formed on the wafer makes continuous contact with the clamping ring in only a few narrow regions that act as conductive bridges when the depositing layer is conductive.